Cleanup upon code inspection in CLion

[KitsuneRal]

Importing Quaternion into CLion was not quite an easy feat (and CLion is still very limited in its CMake support) but once I've done it, I could do some more advanced (static) code inspection than Qt Creator allows. There two basic results from it:

• in general, our code is still better than CLion's support of C++ :) - there were several false "errors" that compile just fine with all our supported compilers; aside from them, the number of warnings about inappropriate code is very low (actually, just 2 warnings, and they are quite bearable).
• having said that, CLion has found a lot of sludge around. Mostly it winds down to stale files and unnecessary #includes. #includes can be safely deleted so I rolled them directly to master; this PR aims to remove most of the remaining extraneous parts. It's not really backwards-compatible; but I don't expect any of you really care about this code though, so no feedback in a week equals to approval.

On a sidenote: running Quaternion (or at least libqmatrixclient) through valgrind would be a great endeavour, by the way: so far it's still leaking memory.